Method and apparatus for casting ceramic pieces



Aug. 7, 1928. 1,679,345

A. O. AUSTIN METHOD AND APPARATUS FOR CASTING CERAMIC PIECES Filed July 2, 1926 A T TORNE Yu 25 material, mixed with water,

30 of the mould.

Patented Aug. 7, 1928.

UNITED STATES PATENT, OFFICE."

ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOB,

MANSFIELD, OHIO, A CORPORATION OF NEW JER- rnn OHIO BRASS COMPANY, or

snx.

BY MESNE ASSIGNMENTS, TO

METHOD AND APPARATUS FOR CASTING CERAMIC PIECES.

' Application filedJuly *2, 1926. Serial No. 120,091.

This invention relates to the manufacture of ceramic articles by the casting'method and has for its object the provision of a method and apparatus for casting such articles which will permit the formation of bination and arrangement of parts and by the steps of the process described in the following specification and illustrated 1n the accompanying drawings.

In the drawings- The figure is an elevation of one-half of a mould showing the formed piece and core in section.

In the casting method of form ng ceram c articles the slip, consisting of the ceramic is placed in a porous mould commonly made of plaster of aris, and the ceramic materlal permitted to be deposited on the inner surface of the mould as the water is absorbed by the wall The excess of water on the \inner surface of the cast articles over that 1 in the outer portion tends to cause the articles to crack in drying or warp in drylng or firmg,

The present method tends to equahzethe water in the inner and'the outer port-ions of the deposited layer and permit the forming of articles on a commercialbasis much more economically. In general, the method 40 consists of using a flexible core which can be withdrawn. This core may be made in a variety of materials. One method is to use a rubber core mandrel or a supporting structure.

. ber member causes it to stretch and redure in diameter, thus permitting the removal of the core. Where intricate or delicate p ts are formed, the core may be allowed to remain inthe piece until drying'or hardening is carried to the point where the core can be removedwithout endangering the piece. .In this case, itis necessary that the core be such that it will deform as the ware shrinks which may be supported on a;

After the piece is cast tension on the rub-' -a feed in pipe.

in drying without producing a stress which w1ll cause cracking. The surface of the core also aids in the building up and permits the fillingof the slip in at points so that a solid mass 1s built up without internal defects. The core may be removed and used rei- M peatedly. Frequently recesses or contours can be formed by the core which would otherwise require considerable work in the formmg. A core of the above type may also be used for reducing excess material, thus ef- E fecting. a saving in the material in some cases. The elimination of material in the cast piece at certain points may also permit the forming of a piece which would not otherwise be possible owing to the shrinkage or firing stresses.

The core may be made up in several different ways to cheapen its cost, to insure ac-v curacy or to permit its removal. In some cases, the core may be made entirely out of rubber or material which will deform easily. In other cases, the outer layer of the core may be'baoked up with wax or other material which may be melted out or dissolved after the piece is formed. Where desired, W the core may be relatively thin and after the piece has sufficiently formed, it may be extended or inflated with air, oil or water so that it will press upon the casting slip on the inner face and'squeeze out the surplus water, tending. to equalize the inner surface with the outer.

The figure shows half the mould with a section through the bushing and core used for forming the inner surface of the cast piece. The outside of the piece is formed by the porous mould 11, the two halves of the mould being clamped together by plates 13 with bolts through holes 1 1 or by other suitable means. Dowls 15 register with corresponding holes in the other half of the mould so that the two parts will register.

In the figure the core is made up in three parts. A main supporting member 16 forms the inner part of the core and also serves as Adjacent to member 16 is a layer of material 17 and 18. This material may be wax or may be a rubber tube, it only being essentialthat the material may be readily removed by meltin or drawing out. Covering. the membersfi and 18 and also a portion of themember 16 are envelopes 19 and '20-. The members 19 and 20 have the shape desired on the inside pf the bushing or article 21 to be formed. in forming a piece, the central member 16 with the forming cores or envelopes 19 and 20 together with the filling members and 18 are placed in half the mould. The tubular member 16 is provided with a. flange 22 which registers with the mould so that the core forming the inside of the bushing is maintained in proper relation to the outside. After the composite core has been made up and placed in half the mould the other half is placed over it and the two parts are clamped and held together. l/Vhere heavy pressures are desired, it is usually necessary to back up the moulds with a plate 13. The vent 23 is opened and casting slip is allowed to flow up through the center of the supporting member 16. A slip is fed outward through the holes 24: extending through the wall of the pipe 16 and through the surrounding core members. The piece 21 to be formed builds up owing to the absorption of water by the mould due to capillary attraction, and also by the forcing out of the water where pressure is applied. The outer surface of the core members 19 and 20 maintains the desired contour regardless of the fact that there may be a tendency to bu1ld up more rapidly in certain sections than in others. Considerable control can be obtained in the building up operation by placing the feed in holes 24: opposite the places which tend to form last, although it is not essential that the holes be placed at these points in many cases.

The method has the advantage that a minimum diameter of opening may be maintained and practically any contour regardless of the normal tendency of the slip to build up along other lines. @ne dificulty in forming pieces where solid cores are used is due to the fact that the piece may build up and shut oil the flow of slip to some section of the piece, before a dense piece 15 formed. This section is likely to crack in drying or cause a pocket due to greater shrinkage owing to the presence ofa larger percentage of water or owing to the fact that there may have been a forming of a ocket owing to the lack of sufiicient castmg material reaching the particular point.

Feeding at the proper points in the improved method may be obtained by placing proper holes along the core or even b providing holes entering from the outs1de at points where the piece may be fed. A. feed tube bf this nature is shown at 25. The piece may be formed entirely from the outside or entirely from the core or by a combination of the two wlthout affecting the scope of the invention. After the piece has been built up and it is not possible for slip to flow along the surface, a compact inner surface will still be formed with the imsuevasas proved method owing to the fact that the envelope 19 and 20 will expand from the pressure on the inside. This will tend to drive excess water out of any slip on the adjacent surface and cause a piece of more uniform density to be formed, thus reducing the danger of cracking during drying and eliminate warping. The supporting inner member 16 may be a tube with a few openings or may have a skeleton construction or a number ports 26 which will permit the pressure on the inside to press the outer layers outward and compact the surface. Where the spacing members 17 and 18 are made of wax, the tube or center supporting member 16 is heated by either passing through steam, hot oil, or electrically or by other suitable means. J This softens the layer 17 and 18 and permits the withdrawal of the members 19 and 20 or the removal of the member 16. Where the piece is placed in a warm place, the remaining wax 18 will then be soft enough to permit the yielding of the members 19 and 20 and take care of the deformation of the formed piece as it shrinks. Another method of operation is to make the members 17 and 18 of rubber, making same of suitable shape. These may be in a single piece or in a number of pieces as desired. After the piece of ware is formed and half of the mould is removed the center member and core may be used to support the piece and lift it from the mould. By pulling on the pieces 17 and 18, theycan be readily withdrawn. This permits the removal of the member 16 and the withdrawal of the forming core 19 and 20. Where these pieces are made of rubber, they may readily be removed and used repeatedly. If the rubber is of the right composition, they may be ion stretched, which causes them-to be reduced in diameter and thereby to be withdrawn very readily without harming the piece.

It is, of course, evident in many cases that the pieces 18 and 20 may be combined as well as the pieces 17 and 19. In some cases where the forming core has sufi'icient stiffness, the rigid supporting member 16 may be left out.

There are many articles which may be formed in this way. The use of the core makes the timing in the casting unnecessary, permits a more uniform density throughout the piece and permits the controlling of an inner contour which would not be possible in the ordinary casting method, except where the cores are of such shape that they may be readily removed. The method used permits the removal of a core without disturbing the piece which is not possible with the ordinary rigid core except for the simple shapes and for cores having considerable draft. The method consists essentially of having a core of sufficient rigidity to form the contour desired and which has sufiicient flexibility so that it can be withdrawn, or,

its

age of the piece.

if left in the piece allowed to contract without setting up undue stress owing to shrink- The flexibility of the core also makes it possible to thoroughly compact the inner surface.-

I claim- 1. The method of manufacturing ceramic articles comprising the steps of depositing plastic material from a slip about a yielding core and removing the core from'the formed piece.

'2. The method of casting ceramic articles comprising the steps of arranging a yielding core Within a porous mould, introducing slip into the space between said core and mould to cause said space to be filled with deposited material from said slip, contracting said core and removing same from the piece formed by the deposit of the material from saidslip.

3. The method of casting ceramic articles comprising the steps of depositing material about a yielding core and permitting said material to dry, said core being compressed during the drying process to prevent undue stress in the formed piece.

4. The method of casting ceramic articles comprising the steps of-arranging a core of yieldin material in a mould of porous material, introducing slip into said. mould to fill the space between'said mould and core with material from said slip removing the formed piece from said mould and'permitting said iece to dry with a portion of said core in p ace, said core yielding to contraction of said formed piece during the drying operation. I

5. The method of casting ceramic articles comprising the steps of arranging a core within a mould, depositing material in the space between said core and mould after the core is in place in the mould and exerting pressure on the interior of said core to press said core against the deposited material.

6. The method of casting ceramic articles comprising the steps of arranging a yielding core Within a porous mould, introducing slip into said mould to fill the space between said core and mould with material deposited from said slip and introducing pressure on the interior of said core to press said core outwardly against the inner face of the material deposited in said mould, thus placing the material under pressure and expelling water therefrom. I

7. The methodof forming ceramic articles comprising the ,steps of arranging a core comprising inner and outer core sections within a porous mould, depositing material between said core and mould and removing said core sectlons successively from sa1 mould.

8. The method of forming ceramic articles comprising the steps of 'arranging a sectional core having portions made of yielding material within a porous mould, introterial deposited from said slip exerting pressure on the interior of said core to compress the material deposited from said slip and expell excess moisture therefrom, removing the formed piece from the mould, contract- 1 ing the core and removing the core from the .formed piece.. i

10. A mould comprising an outer portion of porous material and a core of yielding material having a definite shape inherent in said core.

11. A mouldcomprising an outer portion of porous material and a core having a central supporting portion and a covering of yielding material, the outer surface of said covering having inherently the contour of the interiorof the article to be moulded.

12. A mould comprising an outer portion of porous material and acore having a central supporting section, an outer layer of yielding material and a removable section between saidcentral supporting section and outer layer.

13. A mould comprising an outer portion of porous material and a core having a hollow central support, an outer layer of yielding material and a removable section interposed between 1 said central support and outer layer, the walls of said core being perforated to permit introduction of slip into the space between said core and the surrounding mould.

14. A mould comprising an outer portion of porous material and a central core, said outer portion and core, each having an opening therethrough for into said'mould.

15. A mould comprising an outer portion of orous material and a core having a centheintroducing of slip I tra opening, the outersurface of said core being yielding, said core and outer portion having passages therein for the introducing -of slip into said mould.

In testimony whereof I have signed my name to this specification on this 29th day of June, A. D. 1926.

v ARTHUR o. AUSTIN. 

